This invention relates to a cyclopentylene compound useful as a material for encapsulating electronic devices, for lamination or for adhesion, an epoxy resin composition and a molding material for encapsulating electronic devices which composition and material contain the compound, and a resin-encapsulated electronic device encapsulated with the composition.
Molding materials containing epoxy resin are commonly put into wide use for the encapsulating of electronic devices such as transistors and ICs (integrated circuits). This is because the epoxy resin is well balanced in various properties such as electrical properties, moisture resistance, thermal resistance, mechanical properties and adhesion to inserts. In particular, a combination of o-cresol novolak epoxy resin with phenol novolak curing agent is very well balanced in these properties, and hence widely used as a base resin for IC-encapsulating molding materials.
In recent years, as electronic devices have come to be packaged in a high density, conventional packages of a pin-insertion type have shifted to packages of a surface-mounting type, and the latter is prevailing. In surface-mounting ICs, packages show a tendency to be made thin and compact so that packaging density can be made higher and packaging height can be made smaller. Accordingly, encapsulating mediums have come to be applied in a very small thickness because the volume held by device elements in a package must be made relatively larger.
Such surface-mounting packages differ from the conventional pin-insertion packages in the manner of packaging. In a packaging step for the pin-insertion packages, pins are inserted to a wiring board and thereafter these are soldered on the back of the wiring board. Hence, device elements are by no means directly exposed to high temperature. On the other hand, in a packaging step for the surface-mounting package, devices are provisionally fastened to the surface of a wiring board and then soldered by means of a solder bath or a reflowing assembly. Hence, the device elements are exposed to high temperature. As the result, in instances where a package has moistened, the absorbed moisture may expand abruptly at the time of soldering to crack the package. At present, this phenomenon is a serious problem in the fabrication of surface-mounting ICs.
In IC packages encapsulated with a usual base resin composition, the above problem is unavoidable. Hence, measures are taken such that ICs are moistureproof-wrapped to send them, or ICs are beforehand well dried to use them and then mounted on a wiring board. These measures, however, take much time and also require a high cost.
Accordingly, IC-encapsulating molding materials making use of a biphenyl skeleton type epoxy resin having a good moisture absorption and moisture resistance have been put into practical use for thin-type packages, because of its superior reflow crack resistance. This biphenyl skeleton type epoxy resin, however, has a problem that it has a low Tg (glass transition temperature), and there are limits within which this resin is usable.
The present invention was made taking account of the above problem. A first object of the present invention is to provide a novel compound and an intermediate thereof which are suited as an encapsulating material for electronic devices, having high general-purpose properties, being low moisture-absorptive, having a high adhesion and being rich in fluidity.
A second object of the present invention is to provide a molding material which enables to solder without taking any measure against moisture absorption, e.g., any special pretreatment or wrapping, and a resin-encapsulated electronic device whose elements have been encapsulated with the molding material.
The present inventors have discovered that a cyclopentenylphenol compound obtained by allowing cyclopentadiene to react with a naphthol compound, a phenol compound and/or a fluorene compound in the presence of a specific acid under specific reaction conditions is effective for solving the above problem, and, on the basis of this discovery, they have accomplished the present invention.
To achieve the first object, the present invention provides a first cyclopentylene compound represented by the following general formula (I) (hereinafter xe2x80x9ccompound Ixe2x80x9d) and a second cyclopentylene compound represented by the following general formula (II) (hereinafter xe2x80x9ccompound IIxe2x80x9d). 
In these formulae, m represents a positive number. Ar1 represents at least one of monovalent organic groups represented respectively by 
Ar2 represents at least one of divalent organic groups selected from a first atomic group represented by 
a second atomic group represented by 
and a third atomic group represented by 
In the foregoing, X represents a hydroxyl group, or a 2,3-epoxypropoxyl group (i.e., a glycidyloxyl group) 
Y represents a hydrogen atom, a hydroxyl group or a 2,3-epoxypropoxyl group. Here, R1 to R4 are each a group selected independently from a hydrogen atom, an alkyl group and an aryl group having 1 to 10 carbon atoms, and a halogen atom, and at least one of them may preferably be a hydrogen atom. Z represents a hydrogen atom, a phenyl group, a hydroxyphenyl group or a 2,3-epoxypropoxyphenyl group. In view of readiness for production, Z may preferably be a 4-hydroxyphenyl group or a 4-(2,3-epoxypropoxy)phenyl group.
There are no particular limitations on the position at which the cyclopentylene group is bonded to the naphthalene ring and the benzene ring. For example, in the case of fluorenes, the cyclopentylene group may be bonded to the 3- or 5-position, the 2-position or the 3-position when the hydroxyl group is bonded at the 2-position, the 3-position or the 4-position of the benzene ring, respectively. Such fluorenes can be relatively readily synthesized and are preferred.
The number m of repeating units may preferably be not more than 20 on the average, and particularly preferably not more than 10 on the average, in order to materialize in the compound I the above prescribed properties in a well balanced state. Also, the groups Ar2 in one molecule may all be like atomic groups, or two or more of the first to third atomic groups may be contained in one molecule.
In the case of a compound containing two or more atomic groups (i.e., a cooligomer), its form of polymerization may be any of a random copolymer, an alternating copolymer, a block copolymer and a graft copolymer. In the case of a cooligomer containing the both first and second atomic groups, the number of first atomic groups and the number of second atomic groups in one molecule may preferably be in a ratio of from 20:1 to 1:20, and particularly preferably from 10:1 to 1:10.
In particular, in the molding material for encapsulating electronic devices, when the cyclopentylene compound of the present invention having a phenolic hydroxyl group is used as an epoxy resin curing agent, the above polymerization ratio (number of first atomic groups number of second atomic groups) may particularly preferably be 2:1 to 1:9, and, when the cyclopentylene compound of the present invention in which X is a 2,3-epoxypropoxyl group is used as an epoxy resin, the ratio may particularly preferably be 4:1 to 1:4.
A compound containing as the groups Ar2 the third atomic group in addition to the first atomic group and/or the second atomic group is particularly preferred because of its superior thermal resistance. This third atomic group may preferably be in a content of from 10 to 20 mol % of the total number of groups Ar2 in the molecule.
The present invention also provides as an intermediate for producing the above cyclopentylene compound a cyclopentenyl compound represented by the following general formula (III). 
wherein Ar1 represents any one of monovalent organic groups represented respectively by 
X, Y, Z and R1 to R4 are the same as defined in the case of Formulae (I) and (II).
In the above general formula (III), the cyclopentenyl group 
may preferably be a 2-cyclopenten-1-yl group in view of the reactivity in synthesizing the cyclopentylene compound, and may also be a 3-cyclopenten-1-yl group.
The cyclopentylene compound of the present invention may be used as a component of the epoxy resin composition as an epoxy resin curing agent when it contains a phenolic hydroxyl group and as an epoxy resin when it contains a 2,3-epoxypropoxyl group. Accordingly, in order to achieve the above second object, the present invention provides;
(1) an epoxy resin composition comprising a modified phenol resin which is a first and/or second cyclopentylene compound wherein at least one of X, Y and Z is a phenolic hydroxyl group (hereinafter xe2x80x9ccompound Ia, IIaxe2x80x9d, respectively), and an epoxy resin having two or more epoxy groups in one molecule; and
(2) an epoxy resin composition comprising an epoxy resin which is a first and/or second cyclopentylene compound wherein at least one of X, Y and Z is a 2,3-epoxypropoxyphenyl group (hereinafter xe2x80x9ccompound Ib, IIbxe2x80x9d, respectively), and an epoxy resin curing agent.
The epoxy resin composition of the present invention has superior low moisture absorption, superior fluidity at the time of molding and superior thermal resistance together, and hence can be used in a wide range of fields as a material for encapsulating electronic devices, and also as an anisotropic conductive film material, an insulating material, a laminated sheet material, an adhesive and so forth.
The cyclopentylene compound and epoxy resin composition of the present invention are especially suited for use in materials for encapsulating electronic devices. Accordingly, the present invention provides an epoxy resin molding material for encapsulating electronic devices which contains the first and/or second cyclopentylene compound(s) (compound I, II), and also provides a resin-encapsulated electronic device comprising a device element encapsulated with an encapsulating member containing a cured product of the molding material.